Longest match wins in per-meter default implementation

Author: shakuzen

Diff for: implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpMeterRegistry.java

@@ -16,6 +16,7 @@
 package io.micrometer.registry.otlp;
 
 import io.micrometer.common.lang.Nullable;
+import io.micrometer.common.util.StringUtils;
 import io.micrometer.common.util.internal.logging.InternalLogger;
 import io.micrometer.common.util.internal.logging.InternalLoggerFactory;
 import io.micrometer.core.instrument.*;
@@ -50,6 +51,7 @@
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
 import java.util.function.ToDoubleFunction;
 import java.util.function.ToLongFunction;
 
@@ -503,22 +505,35 @@ static double[] getSloWithPositiveInf(DistributionStatisticConfig distributionSt
         return sloWithPositiveInf;
     }
 
-    private static HistogramFlavor histogramFlavorPerMeter(OtlpConfig config, Meter.Id id) {
-        for (Map.Entry<String, HistogramFlavor> entry : config.histogramFlavorPerMeter().entrySet()) {
-            if (id.getName().startsWith(entry.getKey())) {
-                return entry.getValue();
-            }
+    // VisibleForTesting
+    static HistogramFlavor histogramFlavorPerMeter(OtlpConfig config, Meter.Id id) {
+        return lookup(config.histogramFlavorPerMeter(), id, config.histogramFlavor());
+    }
+
+    // VisibleForTesting
+    static Integer maxBucketsPerMeter(OtlpConfig config, Meter.Id id) {
+        return lookup(config.maxBucketsPerMeter(), id, config.maxBucketCount());
+    }
+
+    private static <T> T lookup(Map<String, T> values, Meter.Id id, T defaultValue) {
+        if (values.isEmpty()) {
+            return defaultValue;
         }
-        return config.histogramFlavor();
+        return doLookup(values, id, () -> defaultValue);
     }
 
-    private static Integer maxBucketsPerMeter(OtlpConfig config, Meter.Id id) {
-        for (Map.Entry<String, Integer> entry : config.maxBucketsPerMeter().entrySet()) {
-            if (id.getName().startsWith(entry.getKey())) {
-                return entry.getValue();
+    private static <T> T doLookup(Map<String, T> values, Meter.Id id, Supplier<T> defaultValue) {
+        String name = id.getName();
+        while (StringUtils.isNotEmpty(name)) {
+            T result = values.get(name);
+            if (result != null) {
+                return result;
             }
+            int lastDot = name.lastIndexOf('.');
+            name = (lastDot != -1) ? name.substring(0, lastDot) : "";
         }
-        return config.maxBucketCount();
+
+        return defaultValue.get();
     }
 
     /**

Diff for: implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpMeterRegistryTest.java

@@ -914,6 +914,52 @@ public Map<String, Integer> maxBucketsPerMeter() {
             .hasSize(56);
     }
 
+    @Test
+    void longestMatchWinsByDefaultHistogramFlavorPerMeter() {
+        Map<String, HistogramFlavor> histogramFlavorPerMeter = new HashMap<>();
+        histogramFlavorPerMeter.put("http", EXPLICIT_BUCKET_HISTOGRAM);
+        histogramFlavorPerMeter.put("http.server", BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+        OtlpConfig config = new OtlpConfig() {
+            @Override
+            public String get(String key) {
+                return null;
+            }
+
+            @Override
+            public Map<String, HistogramFlavor> histogramFlavorPerMeter() {
+                return histogramFlavorPerMeter;
+            }
+        };
+
+        assertThat(OtlpMeterRegistry.histogramFlavorPerMeter(config, createIdWithName("http.server.requests")))
+            .isEqualTo(BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+    }
+
+    @Test
+    void longestMatchWinsByDefaultMaxBucketsPerMeter() {
+        Map<String, Integer> maxBucketsPerMeter = new HashMap<>();
+        maxBucketsPerMeter.put("http", 10);
+        maxBucketsPerMeter.put("http.server", 20);
+        OtlpConfig config = new OtlpConfig() {
+            @Override
+            public String get(String key) {
+                return null;
+            }
+
+            @Override
+            public Map<String, Integer> maxBucketsPerMeter() {
+                return maxBucketsPerMeter;
+            }
+        };
+
+        assertThat(OtlpMeterRegistry.maxBucketsPerMeter(config, createIdWithName("http.server.requests")))
+            .isEqualTo(20);
+    }
+
+    private Meter.Id createIdWithName(String name) {
+        return new Meter.Id(name, Tags.empty(), null, null, Meter.Type.OTHER);
+    }
+
     protected Metric writeToMetric(Meter meter) {
         OtlpMetricConverter otlpMetricConverter = new OtlpMetricConverter(clock, otlpConfig().step(),
                 registry.getBaseTimeUnit(), otlpConfig().aggregationTemporality(),